Human-machine interfaces that are used to translate human movements to machine movements are used in myriad industries. For example, some aircraft flight control systems include a human-machine interface in the form of one or more control sticks. The flight control system, in response to input forces supplied to the control stick from the pilot, controls the movements of various aircraft flight control surfaces. No matter the particular end-use system, the human-machine interface preferably includes some type of haptic feedback mechanism back through the interface to the interface operator (e.g., pilot or co-pilot). In some implementations, the haptic feedback mechanisms are active mechanisms that include one or more electrically controlled motors that supply force feedback to the human-machine interface, typically via multiple gear stages that exhibit relatively high gear ratios.
Although useful and robust, feedback mechanisms that include multiple gear stages do exhibit certain drawbacks. For example, these gear stages, which are typically implemented using multi-stage planetary gears or harmonic drives, increase overall feedback mechanism inertia and friction, which can adversely affect overall system efficiency. Moreover, these multiple gear stages can be relatively heavy and complex and, as a result, relatively expensive. There has thus been a desire to use relatively lighter and less complex mechanisms for interconnecting the motors and the control stick.
One solution that has been proposed is to replace the gear stages with a rope drive system. This solution, however, exhibits its own drawbacks, which are typically associated with the manner in which the rope is anchored. In particular, the rope can exhibit poor adjustability, and over time may exhibit creep (stretching), breakage, thermal growth (shrinkage), and backlash (loss of tension). Hence, there is a need for a rope drive anchoring system that addresses at least these drawbacks.